The present invention is directed to an emergency breathing apparatus of the type which includes a protective suit, first and second sources of air, and a valve for selectively directing the air from either of the first and second air sources to an inhalation orifice of the protective suit. A wearer of the protective suit is normally supplied air from the first air source through a relatively long (100 feet) hose or conduit, but should the latter rupture, a valve can be manually operated to cut-off the air flow to the valve from the first hose and cut-in air from the second air source, such as a compressed air tank, to the inhalation orifice of the protective suit. Accordingly, should the first hose to the first air source break or rupture, the secondary air source provides the user a sufficient time period (10 to 30 minutes) to complete whatever might be the task assigned and/or leave the area before the secondary air source has been depleted.